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BQ33100: Difference in Offset from New Datasheet and Old Datasheet

Louie
Expert 3180 points
Part Number: BQ33100
Other Parts Discussed in Thread: BQEVSW,

Hello,

I have a customer who has seen this:

Calibration (Data section) offset:

We found a gap between the calibration offsets values as listed in the old datasheet comparing to the new datasheet.

As we see in the listed datasheet snapshots, there is a shift in the calibration fields starting from offset 24. For example, in the new datasheet, ‘cc offset’ is located at offset 26 while according to the old datasheet it is located at offset 24.

In our implementation only “CC offset” and “board offset” are affected (zero values of other fields)
Field 104:24 = 0x00    // Board Offset
Field 104:25 = 0x00    // Board Offset
Field 104:26 = 0x59   // CC Offset
Field 104:27 = 0x0c   // CC Offset
Field 104:28 = 0x00
Field 104:29 = 0x00
Field 104:30 = 0x00

We can see that offset 26-27 (cc offset) is not zero as it should be but has the value of 'board offset'.

(1) Can you please explain where does this gap came from ?

(2) Can you please describe what is the impact of mixing between CC and Board offset ?

(3) Up to how many Bytes is they size of the volatile and non-volatile memory?

They are using:

1-      The bqEVSW tool version is : 0.9.92.

2-      The firmware version is :  0x0015 – reading the firmware version via ManufacturerAccess register using command 0x2 as it mentioned in the BQ datasheet.

Could you please help answer the bolded questioned?

  • 0
    TI__Genius 10830 points
    hi Louie,
    This ticket has been assigned to our bq33100 AE. He is on a business trip so may not be able to answer right away.

    Regards,
    David
  • 0 in reply to David Hien
    TI__Mastermind 25955 points
    Hi Louie,

    Due to loading and time required in the lab, please expect an update by Wednesday.

    Sincerely,
    Bryan Kahler
  • 0 in reply to Bryan Kahler
    TI__Mastermind 25955 points
    Hi Louie,

    Thank you for providing the firmware version and EVSW tool version.

    Is an error also being seen in the device, or just a shift in offset? What is the value of CC Offset time in this device? Numbers less than 250 for CC Offset time can cause a CC Offset error.

    1. To aid in answering this question, please provide the SENC file from the device as well as answering the following questions: Also, describe your programming procedure for the CC offset and board offset values. Have these values been manually set? Has the device run through a cycle and been allowed to automatically calibrate the CC Offset prior to entering shutdown? Was this offset *** seen prior to and/or after manual programming? Was this offset seen prior to and/or after automatic calibration?

    2. Two offsets are used for calibrating the offset of the internal coulomb counter, board layout, sense resistor, copper traces, and other offsets from the coulomb counter readings. CC Offset is the calibration value that primarily corrects for the offset error of the coulomb counter circuitry. Board offset is the calibration value used to calibrate all that the CC offset does not calibrate for, including: board layout, sense resistor, copper traces and other offsets external to the device.

    3. This information is not disclosed, but is at least the size of the sum of the known memory contents, as disclosed in the datasheet.

    Sincerely,
    Bryan Kahler
  • 0 in reply to Bryan Kahler
    TI__Expert 3180 points

    Hello Bryan,

    I believe there has been a misunderstanding:

    1. what is the impact of CC offset and Board offset ?
    2. today written in CC offset the value: 0x590c instead of 0 what is the impact of that?   
    3. today written in board offset the value: 0  instead of 0x590c what is the impact of this change?  

    Thank you,

    John Louie

  • 0 in reply to Louie
    TI__Genius 14985 points
    Hi John,
    CC Offset is the internal offset of the coulomb counter circuit block. It is periodically auto-calibrated by the gauge so it does not need to be written. As the datasheet says, "TI does not recommend to manually change this value."
    Board Offset represents any offset to the current measurement and coulomb count outside of the internal coulomb counter circuit block. Use the GUI to perform calibration on some samples of actual production PCBs, read the values of Board Offset, take the average, and use that fixed value for every board in production. The datasheet says, "TI recommends to use characterization data of the actual PCB to set this value." Some customers might be fine leaving it at 0.
    If either CC Offset or Board Offset are very wrong and large, the gauge might falsely report a small current even when no current is present. This will mess up the coulomb count and cause problems.